Expansible two layer linkage having resilient connectors



May 29, 1962 H. KNooP 3,036,425

EXPANSBLE TWO LAYER LINKAGE HAVING RESILIENT CONNECTORS Filed Oct. 24, 1960 FigJ 2 Sheets-Sheet 1 111 72 I V "1 I 1I l' .lh J, 7L '//0 IN VEN TOR:

H. KNOOP May 29, 1962 EXPANSIBLE TWO LAYER LINKAGE HAVING RESILIENT CONNECTORS 2 Sheets-Sheet 2 Filed Oct. 24, 1960 INVENTORZ l BY I //4 l" I v 3,036,425 EXPANSIBLE TW() LAYER LINKAGE HAVING RESILIENT CNNECTRS Hendrikus Knoop, Utrecht, Netherlands, assigner to Rodi & Wienenberger Aktiengesellschaft, `Pforzheim, Germany, a corporation ot Germany Filed Oct. 24, 1960, Ser. No. 64,366 Claims priority, application Netherlands Nov. 2, 1959 7 Claims. (Cl. Sii- 79) The present invention relates to improvements in expansible link straps, particularly for wrist watches, of the type which consists of two superimposed layers of links whichtare offset relative to each other in the longitudinal direction of the strap, and of connecting brackets in the form of spring elements which connect each link of one layer With a link of the other layer and are adapted to be pivoted relative to the links of both layers against spring action, thus tending to maintain the strap in the contracted position.

The principal objects of the present invention are to improve a link strap of the above-mentioned type in a manner so as to permit the strap to he made of smaller elements, to be more inexpensively manufactured, to be more easily assembled or taken apart, to he expanded to a greater length, and, even when expanded, to present a closed appearance toward the outside. j

These objects are attained according to the invention by designing the spring elements in the form of leaf springs which have a width so as to extend across the entire width of the strap and each of which is bent so as to form a slotted tube in which the slot of this tube is defined by opposite edge portions which are disposed within dilerent planes and resiliently engage with and clamp from opposite sides upon angularly bent tongues which are provided on the outer edges of a link of one layer transverse to the direction of expansion of the strap. For attaining the above-mentioned objects the wall of each tubular spring element is further provided at a point spaced from one of the mentioned edge portions with an aperture into which an inwardly bent end of a U-shaped link of the other layer may be hooked which connects two adjacent spring elements pivotably to each other.

According to the invention, one of the edge portions of the spring element is preferably bent at a right angle and 'inserted transversely to the longitudinal direction of the strap into a receiving channel which is formed by tongues which are provided on a link of one layerand arerolset relative to each other. One of the parts which are thus inserted into each other is provided with a tongue which may be bent so as to engage into a corresponding opening in the other part, whereby the two parts are prevented from shifting in a transverse direction relative to each other. In order to facilitate the assembly of the strap as well as the operations of shortening or lengthening the same, it is advisable to design the spring elements so that the opposite edge portions of the two spring elements which are connected to the same link of one layer extend substantially parallel to the direction of expansion of the strap and above the central part of this link when the strap is in the contracted position, so that when the strap is expanded and the spring elements are pivoted, these edge portions will be inclined relative to the mentioned central part and, together with the central part, they will enclose a channel into which a pin may be inserted in a direction transverse to the direction` of expansion of the strap. This pin will maintain two adjacent spring elements in the pivoted position and prevent them from pivoting back to their substantially vertical position, and it will thereby permit the links of the other layer which are hooked into the apertures in the spring ele- SQSAZS Patented May 29, 1962 ments to he easily unhooked therefrom or to be again easily hooked into the apertures.

Each of the two spring elements which are connected to the same link of one layer may also be provided 4with an aperture in the edge portion facing toward the corresponding edge portion of the other spring element, while a pair of tongues project from the two ends of the link and engage into them when the strap is being expanded. The apertures are provided in such a position that, vwhen the strap is being expanded to a certain extent,the two projecting tongues on the link will engage with the edges of the apertures and will thereby limit the extent to which the two spring elements may be pivoted and thus also the extent to which the strap may be expanded.

lln order to give the strap a more closed appearance it is also possible to cover the two longitudinal sides of the strap by providing the ends of the links of the upper layer which are made in the form of substantially U- shaped bars, with outer wall portions which overlap the open ends of the spring elements and possibly also the ends of the links of the lower layer.

These and further objects, features, and advantages of the present invention will become more clearly apparent from the following detailed description thereof, particularly when the same is read with reference to the accompanyin g drawings, in which- `FIGURE 1 shows a longitudinal section of a part of a link strap according to a rst embodiment of the invention;

FIGURE 2 shows a cross section taken along line II- II of FIGURE 1;

FlGURE 3 shows a cross section taken along line lll-III of FIGURE 1;

FIGURE 4 is a perspective view of the spring incorporated in the link strap of FIGURES 1 to 3;

:FIGURE 5 shows a diagrammatic illustration of parts of a link strap according to a modification of the invention Iin the extended position;

FlGURE 6 shows a diagrammatic illustration of the parts of the link strap according to FIGURE 4, but in the contracted position; while FIGURE 7 shows a perspective view of a further moditication of one link member of the strap according to the invention.

Referring tirst particularly to FIGURES 1 to 4 of the drawings, the strap according to the invention consists of one layer of `inks 1, another layer of links 2 which are disposed underneath links '1 and are olfset in the longitudinal direction of the strap relative to links 1, and spring elements 3 which pivotally connect two adjacent links l and 2 of the two llayers to each other.

Each spring element 3 is made of a substantially at leaf spring which is bent into a slotted tubular shape of a substantially rectangular cross section. The longitudinal axis of this tubular spring element extends in a direction transverse to the ldirection of the expansion of the strap. The edge portions 8 and 9 which deine the slot of each spring element 3 are disposed within dilierent planes and enclose and engage under spring tension with projecting tongues on links 2 which extend transverse to the direction of expansion of the strap, thereby forming a force couple which acts upon each link 2. The edge portions 8 and 9 of spring elements 3 also form a pivotal connection with links 2..

For this purpose, each link 2 is provided with a pair of tongues 4 which are bent upwardly at substantially right angles and extend transverse to the direction of expansion of the strap, with a pair of tongues 6 which are disposed within the plane of the central part 5 of link 2, and with tongues "7 which are produced by being bent twice Vat substantially right angles and which extend parallel to the plane of the central part 5. Tongues 4, 6 and 7 form wall portions of a U-shaped receiving channel into which the angularly bent edge portion S of one of the spring elements y3l engages. Theother edge portion 9 of springelernent 3 is likewise bent over at an angle and bears upon the rear Wallof the U-shaped receiving channel.

When the link strap is being assembled, spring elements 3 may be inserted in a direction transverse to the direction of the strap into the receiving channels which are formed by tongues 4, 6 `and 7 of links 2. After each spring element 3 is thus inserted, a tongue 10 at the central part of link 2 within the plane of tongues 6 is bent over so that this tongue 10 then engages into a corresponding opening I1' in the edge portion 8 of spring element 3 and thereby prevents the spring element from shifting transversely. Tonguesv lare illustrated in the drawings in the position before being bent over. Y

After tongues 10 are bent over, spring elements 3 can only carry lout -a pivoting movement relative to the associated links 2, and since their edge portions 8 and 9 are disposed at different planes opposite to each other spring elements 3 will oppose the expansion of the strap during this pivoting movement by a force couple.

Each link 2 is provided in the manner as described with a pair of spr-ing elements 3 at the opposite edges extending transverse to the direction of expansion of the strap, and these two spring elements of each pair are arranged in anV inversely symmetrical relation to each other. Together with one pair of vspring elements 3, each link 2 forms a structural unit which, in turn, is connected to the two adjacent units by a pair of links l which are made substantially in the formrof U`shaped bars. For connecting links 1 to spring elements 3, the transverse sides 12 of links 1 which are bent downwardly at right to the details of such embodiments, but is capable of angleshave at each central part thereof a projecting tongue 13 which is bent inwardly at a right angle and is hooked into an aperture 14 iny one of the spring elements 3 in which it is maintained by the spring tension of spring elements 3. Y

- Tongues 13 of links 1 may be very easily hooked into or unhooked from spring eiements 3 when a pairV of the latter is held temporarily in the pivoted condition as indicated at the right side of FIGURE l, For this purpose it is merely necessary after the strap has been expanded to insert a pin 15 into the space between the central part v5 of 'a link 2 and the edges 9 of the two associated Vspring elements 3, as indicated in FIGURE 1 in dot'and-dash lines.

'.Asfillustrated in'dotted lines in FIGURE 3, links 1 may also be provided with overlapping side walls which extend in the'longitudinal direction of the strap and form the lateral edges thereof. e

FIGUR-ES 5 and 6 show a modification of the invention in which the links 1 of the lower layer have a shape and function similar to links 1 of the upper layer of the strap according to FIGURES 1 to 3, with links 2 of the upper layer corresponding essentially to links 2 of the lower layer. The tubular bent spring elements 3' are in this case of Aa substantially. triangular cross section. Tongues 4 on the upper links which correspond to tongues 4 in FIGURES l to 3 but are slightly longer are provided with hook-shaped ends 16 which, when spring elements 3 are pivoted, engage'into slots 17 in spring members 3V and thereby limit the extent to which the link strap may be expanded. The tongues 13 and apertures Ifl'rcorrespondk to tonguesr13 and apertures 14, respectively, of the strap according to FIGURES l to 3.

FlGURE'7 shows aV perspective bottom view of a modication of a link 2f which is similar to link 2 as shown in FIGURES l to 3.' The difference between links 2 and 2 consists in the fact that each tongue 7l which correspondsV to tongue 7 is` additionally provided with a downwardly projectingVV end 1S. Due to these ends 18, tongues 4, 6", and 7',', when seen in a direction transnumerous modications Within the scope of the appended claims.

Having thus fully disclosed my invention, what I claim 1. In Van eXpansi-ble link strap having two superimposed layers of links, the links of one layer being otfset relative to the links of the other layer, and connecting brackets pivotably connecting each link of the first layer with adjacent links of the second layer, each of said connecting brackets comprising a leaf spring including a wall with free edge portions bent so as to form a tubular spring having a slot therein between said edge portions, said springs and links having substantially equal dimensions in the direction of the strap width, each link of said `rst layer having angnlarly bent tongues adjacent to the outer edges thereof transversely of said strap, the

edge portions of each said spring adjacent to and definingsaid slot being disposed within diierent planes and resiliently engaging with 4and clamping from opposite sides upon said tongues of one of said outer edges, means on said tongues and edge portionsengaging said springs and said links of said first layer against Vrelative movement in the direction of the thickness of said strap, the wall of each of said Vsprings having an aperture at a point spaced from saidV edge portions, each of said links of the second layerbeing substantially U-shaped and having inwardly bent ends, said ends being vhooked into said apertures in two adjacent springs so as to connect said springs pivotably to each other. Y

2. An expansible link strap as defined in claim 1, in which each link of said lirst layer has additional Ytongues adjacent to the outer edges thereofV transversely of said strap each of which additional tongueslie substantially in the plane of the respective link of said first layer of which Vsuch additional tongue is a part, saidrangularly Abent tongues and said additional tongues being offset relative` to each other so as to form a channel, each of said channels havingran opening facing toward the adjacent link of said first layer, Vone of said edge portions of each spring being bent substantially at a right angle and inserted into said opening of said channel.

3. An expansible link strap las deiined in claim 2, in which adjacent to each of said outer edges of said links of said first layer one4 of the two parts comprising said spring and said link of said first layer has -an opening therein, while the other part has a projecting tongue thereon engaging into said opening so as to prevent both parts from shifting transversely relative to each other.

4. An expansible link strap as dened in claim- 1, in which each of two springs connected to a common link of said rst layer has one of said edge portions disposed adjacent to the corresponding edge portion of the other spring, said adjacent edge portions of said two springs extending parallel "to the direction ofexpansion of said strap and above the central part of said link of said rst layer when said strap is in the contracted position, so that, when said strap is expanded and said two springs yare thereby pivoted in opposite directions away from each other, said adjacent edge portions are inclined relative to said central part, whereby a channel is formed between said adjacent edge portions and said central part into which a pin may be inserted in the transverse direction of said strap for preventingv said two springs from pivoting back to their normall position, whereupon the adjacent links of said second layer may be easily hooked into and unhooked from said apertures in said two springs.

5. An expansible link strap as defined in claim 4, in which each of said adjacent edge portions of said two springs has an aperture, said common link of said first layer connecting said two springs having a projecting tongue on each end engaging into one of said apertures when said strap is being expanded, said apertures being of such a size and disposed in such a position that said tongues will limit the extent of the pivotal movement of said springs and thus also the extent of the expansion of said strap.

6. An expansible link strap as dened in claim 1, in which some of said tongues on each link of said first layer are bent over twice so as to for-n1 U-shaped portions into which a respective edge portion of a respective spring element engages so as to be substantially surrounded thereby.

7. An expansi'ble link strap as defined in claim l, in which said strap has longitudinal sides Iand said links of said second layer form substantially U-shaped `bars having wall portions extending along and overlapping the longitudinal sides of said strap.

No references cited. 

